Zinc, nickel and copper are metals that are necessary in trace amounts for proper functioning of various metalloenzymes in humans and animals. For example, zinc deficiency may be associated with anorexia, impaired immune, neural and reproductive functions. Nickel may act as a co-factor for the absorption of iron in the intestine, and copper deficiencies may lead to neurological problems. However, high levels of these metals are also deleterious to human and animal health.
Overdoses of zinc and some of its compounds such as oxides, sulfates, sulfides and chlorides may cause effects in the respiratory tract such as bronchopneumonia and pneumonitis, developmental defects, inflammatory reactions and even death. Prolonged oral exposure to zinc may cause reduced absorption of copper. Estimates of the minimal risk levels of zinc may range from 77-600 mg/m3 for inhalation and 0.3 mg/kg/day for oral exposure.
Like other heavy metals, nickel overexposure may be associated with a wide variety of toxic effects. Acute effects of nickel toxicity may include respiratory distress and hematuria. Whereas subchronic nickel exposure may lead to hepatic and renal toxicity, chronic nickel exposure may cause adenocarcinoma, immune suppression, genotoxicity and neurotoxicity.
Thus, simple, sensitive and accurate methods for assessing low levels of zinc, nickel, copper in both biological and other sample types are important.